Three-compartment bipolar membrane electrodialysis for splitting of sodium formate into formic acid and sodium hydroxide: Role of diffusion of molecular acid

Abstract

Bipolar membrane electrodialysis is used in three compartment configuration to regenerate formic acid and sodium hydroxide from sodium formate. The preceding study [7] showed that diffusion of molecular formic acid is responsible of the loss of acid current efficiency. The present study shows the following results: the diffusion of molecular formic acid through the bipolar membrane explains quantitatively the presence of sodium formate in the sodium hydroxide solution. The loss of acid current efficiency is due to diffusion of molecular acid through both anion exchange and bipolar membranes. The sodium hydroxide current efficiency is determined by acid diffusion through the bipolar membrane and OHleakage through the cation exchange membrane. The flux of acid diffusion in the membranes is proportional to acid concentration. The transfer coefficients vary with the temperature. A model based on mass balance is proposed to describe the electrodialysis. Some experimental parameters like volume variations are needed. It is seen that, following the model, a low temperature is favourable to the process. So does an increase of current density. The nature of anion exchange membrane also affects diffusion. It is found that PC acid 100 membrane is the less permeable to formic acid among 5 tested membranes. The flux of hydroxide ion through the CMB cation exchange membrane is evaluated.

Influence of Temperature on the Performance of Gas Diffusion Electrodes in the CO2 Reduction Reaction

“…However, it also leads to the transfer of potassium ions through the membrane resulting in a depletion of conductive salt on the anode side (see Figure ). In an industrial process, downstream processing e. g. by using bipolar membrane electrodialysis (BMED) is needed, in order to regenerate the anolyte and to yield formic acid instead of formate . The combination of alkaline electrolysis and BMED is not within the scope of this article and will be addressed in future work.…”

Two-compartment bipolar membrane electrodialysis for splitting of sodium formate into formic acid and sodium hydroxide: Modelling

“…The experiments of diffusion of formic acid from a mixture of formic acid sodium formate were done as described in a previous paper [5].…”

“…The three-compartment electrodialysis was studied and modelled [5]. The mass balance of the three-compartment electrodialysis may be predicted knowing volume variations with current quantity for acid, base and salt solutions.…”

“…The modelling given is very complex. Except [5,10], literature is poor concerning the conversion of sodium formate into formic acid and sodium hydroxide by bipolar membrane electrodialysis.…”

Application of bipolar electrodialysis to E. coli fermentation for simultaneous acetate removal and pH control

“…In principle this approach could be used to directly acidify or basify the fermentation broth without the addition of extraneous chemicals. This technology has been widely used in the production of organic acids (Huang et al 2007;Jaime-Ferrer et al 2008), amino acids (Grib et al 1998) and in the field of environmental protection (Koter and Warszawski 2000). From an operational perspective, the cost of acid or base could be reduced and the process could have reduced requirements with regard to treatment of the spent broth.…”